Wireless networks have been developed into a form of a heterogeneous network (HetNet) to improve general wireless network performance and meet user demands, as well as to efficiently correspond to a relatively higher user's traffic demand in a particular area. The HetNet may be understood as a wireless network in a form where a macrocell and microcells like pico cells, femto cells, Closed Subscriber Group (CSG) cells, etc., are overlapped. For example, the CGS cell refers to a cell that provides a service only to a subscriber group authorized to use the service.
The HetNet environment is affected largely by a huge difference in transmit power between the macrocell and the microcell and interference due to the CSG cell. In the case of the CSG cell among the microcells, only authorized users are serviced and thus the CSG cell interferes with the user of the macrocell. In the case of the pico cells and femto cells among the microcells, the macrocell having relatively large transmit power affects the user of the microcell. Such an effect of interference makes it difficult to determine an optimal time for handover between the macrocell and the microcell.
In the following specification, explanation will be focused on interference between a macrocell and a CSG cell. Since the number of Physical Cell IDs (PCIs) for identification of the CSG cells is limited, PCI confusion may occur between the CSG cells.
Specifically, in the case of CSG cells, a PCI region only for the CSG cells is set and CSG cells located within an area of a single macrocell may use the same PCI. In this case, during handover from the macrocell to a CSG cell, PCI overlapping may occur, in which case a target cell may not be determined only with a PCI of the CSG cell. The PCI overlapping becomes a factor that makes it difficult to correctly identify a CSG cell during handover from the macrocell to the CSG cell.
With rapid advancements in communication services, it is expected that (e.g., thousands to tens of thousands) CSG cells and microcells greater in number than CSG cells (having the maximum number of about 500) distinguishable only with the PCI operate in the service area of a macrocell.
However, it is difficult to check proximity to a microcell, such as a CSG cell or check separation from a microcell in a macrocell, and to correctly identify a microcell, and thus a scheme to address the difficulty is required.